1. Field of the Invention
The invention lies within the polymer sector and relates to the use of olefinically unsaturated compounds of specific structure as emulsifiers in emulsion polymerization.
2. Background Information
Emulsion polymerization is a specific method of polymerization wherein olefinically unsaturated monomers of low solubility in water are emulsified in water by means of emulsifiers and polymerized using water-soluble initiators such as potassium peroxodisulfate or redox initiators for example. Anionic and/or nonionic surfactants are the key constituents here in that they ensure the process of emulsion polymerization via micelle construction in the aqueous solution.
Copolymerizable emulsifiers are in great demand in industry since they are wholly or partly incorporated in the growing polymer chain and thus reduce the migration of free emulsifier molecules in the end-use product for example. Copolymerizable emulsifiers occupy a position halfway between monomers and conventional emulsifiers. Their reactivity has to be tailored to the monomer system used and they must not have an adverse effect on the properties of the polymer formed. At the same time, they must not lose their emulsificative properties as a result of the presence of a reactive group. Owing to this combination of specific properties, novel copolymerizable emulsifiers are greatly sought after in industry.
German laid-open specification DE-A-10340081 describes copolymerizable surfactants of the formula HOOC—CH═CH—COO—(BO)z(PO)y(EO)xR1, where R1 is an alkyl radical or alkylphenol radical having 8 to 24 carbon atoms, BO is a butylene oxide unit, PO is a propylene oxide unit and EO is an ethylene oxide unit, and the numbers x, y and z are each independently 0 or numbers from 1 to 50, with the proviso that at least one of x, y and z is other than 0, wherein the carboxyl group may be wholly or partly present in neutralized form and the C═C double bond may be cis- or trans-configured.